Intelligence and Miscellaneous Articles. 71 



experiments made at the Royal Institution on the manufacture of 

 glass for optical purposes. The investigation was taken up in con- 

 sequence of tiie formation of a conamittee by the Royal Society, and 

 a working sub-committee consisting of Mr. Herschel, Mr. Dollond, 

 and Mr. Faraday. The late researches of the committee have been 

 directed towards the manufacture of a very heavy and fusible glass, 

 which from its optical properties oifered some important advantages 

 over flint glass ; whilst its chemical properties were such as to admit 

 of a process being applied to it that should produce perfectly uniform 

 and homogeneous plates. The general process adopted was descri- 

 bed^; and it was stated, that three telescopes had been manufactured 

 with the plates produced, which gave very good results and strong 

 promise of ultimate success : tiie experiments, however, are still in- 

 complete, but it is supposed a few months will finish them, when a 

 full account will be laid before the parent committee of the Royal 

 Society, and then published. 



Some fine specimens of New-Forest oak timber, which had been 

 experimented upon for tlie purpose of ascertaining their strength, 

 were laid on the library tables, with the description and results 

 of the experiments : also numerous mechanical models. 



This evening concluded the meetings at the Royal Institution for 

 this season. 



XI. Litelligoice a7id Miscellaneous Articles. 



ORIGIN OF CERTAIN ERINE-SPRINGS IN NORTH AMERICA. 



FORMER EXISTENCE OF ROCK-SALT IN THE " SALIFEROUS 

 rock" OF THAT COUNTRY. — STRONG EVIDENCE THAT A 

 HIGH TEMPERATURE WAS CONCERNED IN THE FORMATION 

 OF THE NEVV-RED-SANDSTONE. 



AS Dr. Bigsby, in his interesting sketch of the geology of Lake On- 

 tario (Fhil. Mag. and Annals, for May, p. .341), has mentioned 

 Prof. Eaton's hypothesis, that the brine of the salt-springs in the district 

 adjoining the Erie canal " is produced from elementary materials 

 [the elements of common salt] contained in this [the salifcrous] and 

 higher rocks," it may not be useless to show that Mr. Eaton has ad- 

 duced no real evidence to this effect, and that his account of the geo- 

 logical relations of these springs, in conjunction with Mr. Chilton's 

 analyses of them, alluded to in the paper mentioned in the following 

 notice sufficiently explains their origin. Prof. Eaton first made public 

 his ideas on the subject in Silliman's Journal, vol. vi. p. 242. A 

 specimen of the rock called water-limestone (a limestone subordinate 

 to one of the members of the salifcrous series) which forms the roof 

 of the springs, if pulverized and examined ever so minutely, " pre- 

 sents nothing to the senses," he says, " resembling common salt." 

 ]Jut "on exposing a fresh fracture of a specimen from this rock, for 

 two or three weeks in a damp cellar, it shoots out crystals of common 

 talt, sufficient to cover it;* whole surface." From these facts I'mf. 



Eaton 



